1. Field of the Invention
The invention refers to a coupling device having two coupling parts and clamping means for releasably axial clamping of both coupling parts. A number of non parallel grooves spaced circumferentially are provided within one of both coupling parts as a reference system in a plane perpendicular to the clamping direction. Pins projecting from the surface of the other coupling part and having two opposing lateral surfaces are provided. At least one of the lateral surfaces of each pin includes an angle with the clamping direction.
2. Description of Related Art
In case one of the coupling parts is connected to the head of a machine tool, e.g. an EDM machine, and the other coupling part supports a work piece to be worked upon by the machine, the work piece may be positioned relative to the machine with very high precision within a plane (x-y-plane) perpendicular to the clamping direction (z-direction). The positional deviation amounts to only a few xcexcm even after a very great number of clamping procedures and releasing procedures for the work piece and its coupling part. Such high position is achieved with a coupling device according to EP-A-722 809 (=U.S. Pat. No. 5,791,803) by creating a force acting circumferentially upon the coupling part during clamping.
A counterforce created when machining the workpiece, e.g. when producing a deep recess within the work piece by a lathe, may counteract to such force which may impair maintaining the close positional tolerance.
The invention therefore is based on the object to improve the repeatability precision of the positioning of one coupling part relative to the other coupling part under high load of one of the coupling parts in circumferential direction.
To this end the invention provides for a coupling device according to the above-mentioned type within which at least one clamping plate is disposed at one of the coupling parts such that during clamping it is clamped between one of the lateral surfaces of one of the pins and a flank of a groove cooperating with the pin for obtaining the desired adjustment of both coupling parts. The coupling device according to the invention allows therefore not only for an excellent repeatability of the precise positioning of the coupling parts with respect to each other but exhibits substantial stiffness of the alignment under heavy load which is limited only by the compressibility of the material of the clamping plate.
In a preferred embodiment of the invention the clamping plate is fixedly connected to the coupling part and preferably is integral therewith. Advantageously the clamping plate has a first section extending parallel to the clamping direction, and a second axially elastic section mounted to the associated coupling part.
In an aspect of the invention two clamping plates are provided the second sections of which are combined by a connecting base to form an overall U form configuration. According to one embodiment the base is mounted to a pin of a coupling part from which said pin projects. In an alternative the base is mounted to the bottom of a groove in a coupling part into which the grooves are cut. To this end the bottom may have a projection to which the base is mounted centrally.
According to another aspect of the invention the groove may be extended inwardly and laterally by an undercut. In such case the clamping plate may be made by driving a cut into the body of the coupling part such that the first section of the clamping plate extends in clamping direction and the elastic second section thereof extends transversely into the undercut.
Releasing the clamped coupling parts is simplified if according to another aspect of the invention the flanks of the grooves and/or the pins and/or the clamping plates are provided with hardened surfaces.